[support] "An illegal choice has been detected. Please contact the site administrator" with date module

[Martin Tomes]

I have installed CCK, views and date modules as of today and added a 
date field to a content type.  When I set the date and save a page of 
this type I get this message:

"An illegal choice has been detected. Please contact the site 
administrator."

The date fails to set.

Does anyone have any idea where I might have gone wrong?

-- 
Martin.